Overexpression and/or gene amplification of the epidermal growth factor (EGF) receptor, or EGFR, have been reported in multiple human tumors, including those in breast, ovarian, bladder, brain, and various squamous carcinomas (Wong, A. J. et al., 1987, Proc. Natl. Acad. Sci. USA, 84:6899-6903; Harris et al., 1992, Natl. Cancer Inst. Monogr. 11:181-187). However, targeting the EGFR as an anti-neoplastic therapeutic method has been problematic as many normal tissues also express this receptor and may get targeted along with the neoplastic targets. Meanwhile, it has been reported that many glioblastomas having EGFR gene amplification frequently contain gene rearrangement (Ekstrand, A. J. et al., 1992, Proc. Natl. Acad. Sci. USA, 89:4309-4313; Wong A. J. et al., 1992, Proc. Natl. Acad. Sci. USA, 89:2965-2969). In one study, 17 out of 44 glioblastomas were found to have one or more alterations in the EGFR coding sequence and all of these cases contained amplified EGFR, while none of the 22 cases without gene amplification showed any tumor-specific sequence abnormalities (Frederick, L. et al., 2000, Cancer Res 60:1383-1387). The same study also showed that multiple types of EGFR mutations could be detected in individual tumors.
The class III variant of the EGFR (EGFRvIII) is the most frequently found EGFR variant in glioblastoma (Bigner et al., 1990, Cancer Res 50:8017-8022; Humphrey et al., 1990, Proc Natl Acad Sci USA 87:4207-4211; Yamazaki et al., 1990, Jap J Cancer Res 81:773-779; Ekstrand et al., 1992, Proc Natl Acad Sci USA 89:4309-4313; Wikstrand et al., 1995, Cancer Res 55:3140-3148; and Frederick et al., 2000, Cancer Res 60:1383-1387). EGFRvIII is characterized by a deletion of exons 2-7 of the EGFR gene, resulting in an in-frame deletion of 801 base pairs of the coding region, i.e., deletion of 6-273 amino acid residues (based on the residue numbers of mature EGFR), as well as the generation of a new glycine at the fusion junction (Humphrey et al., 1988, Cancer Res 48:2231-2238; Yamazaki et al., 1990, supra). EGFRvIII has been shown to have a ligand-independent, weak but constitutively active kinase activity as well as enhanced tumorigenicity (Nishikawa et al., 1994, Proc Natl Acad Sci USA 91:7727-7731; and Batra et al., 1995, Cell Growth and Differentiation 6:1251-1259). In addition to gliomas, EGFRvIII has been detected in ductal and intraductal breast carcinoma (Wikstrand et al., 1995, Cancer Res 55:3140-3148), non-small cell lung carcinomas (Garcia de Palazzo et al., 1993, Cancer Res 53:3217-3220), ovarian carcinomas (Moscatello et al., 1995, Cancer Res 55:5536-5539), prostate cancer (Olapade-Olaopa et al., 2000, British J. Cancer 82:186-194), and squamous cell carcinoma of the head and neck (Tinhofer et al., 2011, Clin Cancer Res 17(15):5197-5204). In contrast, these and other studies report that normal tissues do not express EGFRvIII (Garcia de Palazzo et al., 1993, supra; Wikstrand et al., 1995, supra; and Wikstrand et al., 1998, J Neuro Virol 4:148-158). The highly tumor-specific nature of EGFRvIII makes it an especially useful target for treating cancers and tumors that express this molecule.
The nucleic acid and amino acid sequences of human EGFR are shown in SEQ ID NOs: 145 and 146, respectively, and the amino acid sequence of EGFRvIII is shown in SEQ ID NO:147. Antibodies to EGFRvIII are described in, for example, U.S. Pat. No. 5,212,290, U.S. Pat. No. 7,736,644, U.S. Pat. No. 7,589,180 and U.S. Pat. No. 7,767,792.